web/wp-content/themes/mozilla-builders/static/scss/mixins/_font-face.scss

@mixin face($family-name, $file-name, $font-weight: normal, $font-style: normal) {
  @font-face {
    $font-path: '../fonts/#{$file-name}';
    font-display: block;
    font-family: '#{$family-name}';
    font-style: $font-style;
    font-weight: $font-weight;
    // src: url($font-path + '.eot?') format('embedded-opentype');
    src:
      url($font-path + '.woff2') format('woff2'),
      url($font-path + '.woff') format('woff');
  }
}